Non-invasive prenatal testing provides information about the condition or health of a fetus using a maternal blood sample or another sample obtained non-invasively from the pregnant female. Early detection of the condition or health of the fetus allows targeted interventions and medical treatments.
Rolling-circle amplification (RCA) is useful for analyzing cell free DNA in maternal blood. However, quantifying RCA products with statistical robustness can be challenging. At a practical level, although the absolute numbers of products in an RCA reaction may be sufficiently high to provide statistical robustness, the molar concentration of specific RCA amplicons in the reaction may be quite low, which limits the types of methods that one can use to quantify them. For example, RCA products in a sample can, in theory, be detected by labeling the RCA products, depositing the sample onto the surface of a glass slide, and counting the number of labeled products on the slide. However, simply placing a solution containing labeled RCA products on a glass slide, allowing the labeled RCA products to diffuse to the surface and then counting the number of labeled RCA products that have attached to the slide takes several hours and not all of the labeled RCA products reach the slide and are counted.
Use of filtration onto a solid support to quantify labeled RCA products is described herein. As will be described in greater detail below, the methods may facilitate analysis of samples containing RCA products.